Do not re throw on a failed Attachment.

[lucas-zimerman]

The code behavior from CaptureEnvelope when capturing an event diverges when an attachment fails to get the stream content.

• With the logger set, the event is sent without the failed attachment and logs a warning about the failed attachment.
• Without the logger set (Debug = false), the events gets dropped by the failed attachment.

This PR fixes the behavior when debug is set to false by only dropping the failed attachment and not the event.

[bruno-garcia]

We took the original approach on Unity and found ourselves in a bad situation but I rather we make the logger required instead of just logging optionally (e.g: when is it null? why?)